ACUTE EFFECTS OF ENDOTOXIN INHALATION ON THE RESPIRATORY-TRACT IN PIGS - INTERACTION WITH AMMONIA

The acute respiratory effects of endotoxin inhalation (0-400 mu g/kg) have been evaluated in pigs. Endotoxin (LPS from Escherichia coli O127 :B8 and O55:B5) nebulization had no direct effect on the nasal mucosa. An in vitro bronchial hyperreactivity to acetylcholine and histamine, related to the endotoxin dosage, was recorded. In the lung, significa nt endotoxin dose-dependent increases in the total cell, alveolar macr ophage, and neutrophil counts in the BAL fluid were recorded. Followin g intrabronchial administration of endotoxin, the cellular response wa s significantly higher than that obtained after nebulization. Neither the dry to wet lung weight ratio (DW/WW) nor the albumin concentration in the BAL fluid war; affected. When endotoxins were infused intraven ously, the lung cellular response was accompanied by an increase in th e albumin concentration in the BAL fluid. In pigs exposed for 6 days t o 50 ppm ammonia, endotoxin nebulization induced a significant increas e in the albumin concentration and tented to increase the number of ne utrophils in the NAL fluid. Ammonia did not alter the lung response to endotoxin inhalation. It was concluded that endotoxin nebulization ca n produce bronchial hyperreactivity and a cellular inflammatory respon se in the lung, but without inducing pulmonary edema. Ammonia can inte rfere with nasal response to endotoxins. The weak response to endotoxi n inhalation could be ascribed to the barrier role played by the alveo lar epithelium and to dilution of the aerosol throughout the respirato ry system.